1. Field of the Invention
The present invention relates to chain conveyers for printing presses, and more particularly to chain conveyors having easily removable block and pusher assemblies to accommodate different sized workpieces.
2. Related Art
Printing presses for printing individual workpieces are well known. U.S. Pat. No. 2,787,214 to Halahan et al is illustrative of such printing presses, and is incorporated herein by reference in its entirety. Another example of such a printing press is the Super Jet.RTM. printing press manufactured by Halm Industries Company, Incorporated of Glen Head, N.Y.
In such printing presses, the workpieces, such as envelopes, are separated by a suction feeding device and then placed by belts on a chain-driven conveyor. The conveyor carries the workpieces downstream to the printing roller, where the workpieces are inserted between the printing roller and an impression roller. The feed chain, which for example is an ASA standard roller chain, has block and pusher assemblies associated therewith for moving the workpieces down the conveyor.
FIG. 1 illustrates a portion of typical prior art feed chain 10 having a block and pusher assembly 20 attached thereto. Block and pusher assembly 20 comprises a block 22 permanently affixed to feed chain 10 and an adjustable pusher 24 removably affixed to block 22. Block 22 is affixed to feed chain 10 by a pair of pins 26 extending transversely through block 22 and through the rollers 28 of one of the links 30 of chain 10.
A recess 32 is provided in the top of block 22 for receiving pusher 24. Pusher 24 is L-shaped with first and second legs 24a and 24b. An elongated slot 40 is formed in first leg 24a. A pusher screw 42 is inserted through slot 40 and engages a threaded bore (not shown) extending longitudinally through block 22. Second leg 24b extends upwardly from block 22 and carries and registers the workpiece, the trailing or rear edge of the workpiece being held against second leg 24b.
Pusher screw 42 is provided with a socket 50 for engagement with a wrench (not shown) for loosening and tightening screw 42. When screw 42 is loosened, the position of pusher 24, and thereby second leg 24b, can be adjusted relative to the leading and trailing ends 22a and 22b of block 22. Screw 42 can also be removed, to permit removal of pusher 24 from block 22.
Conventionally, pusher and block assemblies 20 are spaced apart from each other such that the second legs 24b of their respective pushers 24 are separated from each other by slightly more than the distance between the leading and trailing edges of the smallest workpieces to be processed by the printing press. For example, if the distance between the leading and trailing edges of the smallest workpiece is six inches, then second legs 24b of pushers 24 will be separated by a distance of slightly more than 6 inches.
Because block and pusher assemblies 20 are not removable from feed chain 10, the only way to accommodate larger workpieces is to remove entirely some of pushers 24. For example, to accommodate workpieces having a distance between their leading and trailing edges of more than six inches and up to twelve inches, every other pusher 24 must be removed. This requires unscrewing and removing the pusher screws 42 from every other block and pusher assembly 20. This procedure is labor-intensive, and therefore time-consuming and expensive. It is the solution of this and other problems to which the present invention is directed.